A multimeric immunogen for the induction of immune memory to beta‐amyloid

Abstract

The development of active immunotherapy for Alzheimer's disease (AD) requires the identification of immunogens that can ensure a high titer antibody response toward beta-amyloid, whereas minimizing the risks of a cell-mediated adverse reaction. We describe here two novel anti-beta-amyloid vaccines that consist of 'virus like particles' formed by a domain of the bacterial protein E2 that is able to self-assemble into a 60-mer peptide. Peptides 1-11 and 2-6 of beta-amyloid were displayed as N terminal fusions on the surface of the E2 particles. E2-based vaccines induced a fast-rising, robust and persistent antibody response to beta-amyloid in all vaccinated mice. The immune memory induced by a single administration of vaccine (1-11) E2 can be rapidly mobilized by a single booster injection, leading to a very high serum concentration of anti-beta-amyloid antibodies (above 1 mg ml À1 ). E2 vaccination polarizes the immune response toward the production of the anti-inflammatory cytokine interleukin-4 and does not induce a T cell response to beta-amyloid. Thus, E2-based vaccines are promising candidates for the development of immunotherapy protocols for AD. Alzheimer's disease (AD) is characterized by deposition of insoluble protein aggregates in the brain, known as amyloid plaques, which are mainly composed of beta-amyloid peptide. Active and passive immunization studies performed in transgenic mouse models of beta-amyloid deposition have demonstrated that antibodies against beta-amyloid are able to reduce plaques and improve cognition (reviewed in 1-3 ). In mouse models of AD, induction of a high titer of anti-beta-amyloid antibodies correlated with the therapeutic efficacy of vaccination [4][5][6] A clinical trial of immunization of AD patients with whole preaggregated beta-amyloid peptide has shown that immunization has the potential to reduce amyloid plaques in the brains of AD patients and delay disease progression. 7,8 However, the trial was interrupted when 6% of patients developed an adverse inflammatory reaction involving infiltration of T cells into the brain; moreover, only 59 of 300 individuals who received the vaccine mounted a humoral anti-beta-amyloid response with a titer higher than 1:2200. 9 Individuals with the highest titers of anti-beta-amyloid antibodies demonstrated the most pronounced depletion of plaques. 10 The development of a Th1-type response was found to correlate with an adverse inflammatory reaction. 11 The development of an effective and safe immunotherapy protocol faces two challenges, namely, overcoming the low immunogenicity of the beta-amyloid peptide and avoiding detrimental inflammatory reactions in the brain.The N-terminus of beta-amyloid is considered the most promising antibody target for inclusion in recombinant vaccines. 1 We have previously observed reduced deposition of beta-amyloid plaques in mice that received monthly injections of phage-based vaccine fdAD (2-6), a bacteriophage that displays the epitope AEFRH of betaamyloid as an N terminal fusion to the major capsid p...

Alum and Squalene-Oil-in-Water Emulsion Enhance the Titer and Avidity of Anti-Aβ Antibodies Induced by Multimeric Protein Antigen (1–11)E2, Preserving the Igg1-Skewed Isotype Distribution

“…(1–11)E2 was produced and characterized as previously described [9] and stored at −80°C. To obtain LPS-free (1–11)E2, protein samples were purified from lipopolysaccharide (LPS) by phase separation with TritonX-114 (Sigma) [12], followed by detergent removal with Thermo Scientific Pierce Detergent Removal Resin (Thermo Scientific).…”

“…ELISA assays were performed as previously described [9], [10], [13]. Wells of a 96-well Nunc Immunoplate were coated with 100 µl of 5 µg/ml streptavidin at 37°C over night until complete evaporation.…”

“…We have previously described a multimeric protein antigen for the induction of an antibody response to Aβ that consists of a domain of the bacterial protein E2 able to self-assemble into a particle consisting of 60 monomers [9]. Peptides encompassing the 1–11 and 2–6 amino acid positions of Aβ were displayed as N-terminal fusions on the surface of the E2 particles [9]. E2-based vaccines induced a fast-rising, robust and persistent antibody response to Aβ in all vaccinated mice, with a higher titer of anti-Aβ antibodies in the case of the vaccine harboring the 1–11 Aβ peptide, i.e.…”

“…vaccine (1–11)E2. Balb/c mice receiving (1–11)E2 formulated in Complete Freund's Adjuvant (CFA) developed immune memory to Aβ after a single dose, as demonstrated by the fact that a booster dose, administered 6 months after the first dose, induced a very high serum concentration of anti-Aβ antibodies (above 1 mg/ml) [9]–[11]. Vaccination with (1–11)E2 in Complete Freund's Adjuvant - Incomplete Freund's Adjuvant (CFA-IFA) polarizes the immune response toward the production of the anti-inflammatory cytokine Interleukin-4 and does not induce a T cell response to Aβ [9].…”

“…Compared to our previous study [9] a detoxified (1–11)E2 preparation was employed in this work in order to eliminate potential confounding effects caused by lipopolysaccharide (LPS), a typical contaminant of proteins produced in E. coli and a strong activator of innate immunity.…”